KR20030031148A - Aqueous cross-linkable binder composition and its use in the production of lacquer coatings - Google Patents

Abstract

The present invention relates to an aqueous dispersion of an aldehyde-functional polyurethane wherein (A) the polyurethane comprises an ionic and / or non-ionic disperser, and has a number average molecular weight of at least 1,000 and an average aldehyde functionality of at least two, and

(B) Structural Formulas E ¹ -CHR ¹ -E ² and HC- (E ¹ E ² E ³ ), wherein -E ¹ , -E ² and -E ³ are each -P (= 0) -O-, Is selected from an electron withdrawing group such as -CO-, -CN, -SO _2- , -NO _2, and R ¹ represents a hydrocarbon radical having 1 to 10 carbon atoms or hydrogen; An aqueous crosslinker composition comprising a low molecular weight aldehyde-reactive crosslinker selected from the group of low molecular weight compounds and low molecular weight polyamines, wherein the ionic dispersing group is a carboxylate, sulfonate and / or phosphate (or phosphonate) Anionic dispersing group selected from the group of base groups, and / or the C ₁ -C ₄ alkoxy poly C ₂ -C ₃ alkylene-oxide group in an amount of 2.5 to 20 wt. It is characterized by being used.

Description

AQUEOUS CROSS-LINKABLE BINDER COMPOSITION AND ITS USE IN THE PRODUCTION OF LACQUER COATINGS

The present invention relates to aqueous crosslinker compositions and their use in preparing lacquer coatings.

Aqueous crosslinker compositions comprising aqueous polyurethane dispersions are well known for preparing membrane coatings for various substrates such as metals and plastics. Although a high quality coating layer can be obtained by known aqueous binder compositions, the properties of the aqueous polyurethane dispersions used in the known compositions still leave room for improvement in the automotive refinishing plant. These improvements relate to reducing their excessive foaming, the amount of organic solvent (VOC), the toxicity of one or more components in the binder composition and / or the curing rate at ambient temperature (RT) when applied by spraying. will be.

The present invention provides a binder composition having an acceptable foaming behavior and curing rate at ambient temperature, the composition comprising:

(A) an aqueous dispersion of an aldehyde-functional polyurethane, wherein the polyurethane comprises an ionic and / or non-ionic disperser, and has a number average molecular weight of at least 1,000 and an average aldehyde functionality of at least two, and

(B) Structural Formulas E ¹ -CHR ¹ -E ² and HC- (E ¹ E ² E ³ ), wherein -E ¹ , -E ² and -E ³ are each -P (= 0) -O-, Is selected from an electron withdrawing group such as -CO-, -CN, -SO _2- , -NO _2, and R ¹ represents a hydrocarbon radical having 1 to 10 carbon atoms or hydrogen; A low molecular weight aldehyde-reactive crosslinking agent selected from the group of low molecular weight compounds and low molecular weight polyamines.

It is preferable to provide a crosslinking agent containing an acetoacetate group.

It should also be added that aldehyde-terminated polyurethanes have already been disclosed in US Pat. No. 3,392,148. Curable resins can be used as protective coatings, moldings and adhesives for laminates. The composition is prepared by addition reaction of hydroxy-aldehyde with polyisocyanate. The non-aqueous composition is cured with a material or acid catalyst that will generate an acid upon heating to about 100-200 ° C. or less.

At ambient temperature by adding a low molecular weight crosslinker starting from an aldehyde-terminated polyurethane having a number average molecular weight of at least 1,000 and an average aldehyde functionality of at least two and comprising an ionic and / or non-ionic disperser and containing an aldehyde reactor. It is not mentioned that a curable aqueous crosslinker composition can be obtained.

EP-A-0 332 326 discloses an aqueous self-crosslinkable coating composition comprising an aqueous dispersion comprising at least one polyurethane polymer having a hydrazine-functional group and a carbonyl-functional group. The carbonyl-functional group may or may not be present in the same polyurethane polymer as the hydrazine-functional group.

EP-A-0 367 051 discloses aqueous storage-stable, carbonyl group-containing crosslinkable polyurethane dispersions. The carbonyl group is derived from the addition of diepoxide to hydroxyacetone, hydroxybenzaldehyde, acetoin, benzoin, ketocarboxylic acid. Polyurethanes are dispersed in water in the presence of organic amines such as trimethyl amine, trialkyl amines such as triethyl amine, or hydroxyalkyl amines or ammonia, such as trishydroxyethyl amine, or mixtures thereof. Polyhydrazide is used for the crosslinking agent. However, in using the dispersion for coating purposes, a coating with improved appearance is produced. In addition, polyurethanes based on β-hydroxyketone become unstable over time, and can be decomposed during storage while removing CO ₂ .

EP-A-0 442 652 discloses an aqueous coating composition comprising an aqueous polyurethane dispersion, wherein the polyurethane polymer is 3 so that groups not participating in the chain extension are side carbonyl-containing groups in the chain-expansion polymer. It has a chain-pendant or in-chain groups Y having a chain-extension compound having at least one independently reactive enolyl carbonyl group. Only the chain-extension compounds used in the examples are prepared from trimethylol propane triacetoacetate. Little mention is made of substituting aldehyde groups for the triacetoacetate groups which provide compositions with improved water stability.

EP-A-0 584 818 discloses aqueous self-drying and optionally crosslinkable coating compositions for multilayer lacquering of repaired vehicles. The coating composition comprises an aqueous dispersion of polyurethane resin with a number average molecular weight (Mn) of 2,500 to 1,000,000 containing at least one CH acid group per molecule. Crosslinkers include free or masked polyisocyanates or at least two functional aldehydes having an average of 1.5 isocyanate functional groups per molecule. Preferably the aldehyde is formaldehyde and / or glyoxal and the polyisocyanate is diisocyanate.

WO 96/41833 discloses binder compositions comprising a strongly activated carbanion-functional polymer and an aldehyde group-containing crosslinker. Carbanion-functional groups are preferably acetoacetate groups, malonate groups, acetonate groups or mixtures thereof. The polymer is an alkyd resin or a polyester resin.

Thus, good results were obtained with the aqueous crosslinker composition when the number average molecular weight of the aldehyde-functional polyurethane was 1,000 to 100,000.

It is desirable to provide the binder composition with an aldehyde-functional polyurethane obtainable by reaction of the following materials.

a) organic polyisocyanates,

b) organic compounds containing at least two isocyanate-reactive groups and having a number average molecular weight of 400 to 6,000,

c) (a) single-functional and / or multi-functional isocyanate-reactive compounds containing nonionic and / or ionic dispersers (or groups which can be later converted into dispersers),

d) isocyanate-reactive aldehyde-functional compounds,

e) optionally, an organic polyol having a weight average molecular weight of less than 400, and

f) optionally, an active hydrogen-containing chain expanding material.

Polyisocyanates used to prepare polyurethane polymers are aliphatic, cycloaliphatic or aromatic di-, tri- or tetraisocyanates, such as 1,2-propylene diisocyanate, trimethylene diisocyanate, tetra, which may or may not be ethylenically unsaturated. Methylene diisocyanate, 2,3-butylene diisocyanate, hexamethylene diisocyanate, octamethylene diisocyanate, 2,2,4-trimethyl hexamethylene diisocyanate, 2,4,4-trimethyl hexamethylene diisocyanate, dodecamethylene Diisocyanate, ω, ω'-dipropylether diisocyanate, 1,3-cyclopentane diisocyanate, 1,2-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, isophorone diisocyanate, 4-methyl- 1,3-diisocyanatocyclohexane, trans-vinylidene diisocyane , Dicyclohexyl methane-4,4'-diisocyanate, toluene diisocyanate, 1,3-bis (isocyanatomethyl) benzene, xylene diisocyanate, 1,5-dimethyl-2,4-bis ( 2-isocyanatoethyl) benzene, 1,5-dimethyl-2,4-bis (2-isocyanatoethyl) benzene, 1,3,5-triethyl-2,4-bis (isocyane) Itomethyl) benzene, 4,4'-diisocyanatodiphenyl, 3,3'-dichloro-4,4'-diisocyanatodiphenyl, 3,3'-diphenyl-4,4'-diisocyanai Todiphenyl, 3,3'-dimethoxy-4,4'-diisocyanatodiphenyl, 4,4'-diisocyanatodiphenyl methane, 3,3'-dimethyl-4,4'-diisocyanatodi Adduct of 2 molecules of diisocyanate such as hexamethylene diisocyanate or isophorone diisocyanate to diols such as phenyl methane, diisocyanatonaphthalene, ethylene glycol, 3 molecules of hexamethylene diisocyanate to 1 molecule of water Adducts (available as Desmodur N manufactured by Bayer), adduct of 1 molecule of trimethylol propane to 3 molecules of toluene diisocyanate (available as Desmodur L manufactured by Bayer), 3 molecules of isophorone diisocyanate Adduct of 1 molecule of trimethylol propane for, compounds such as 1,3,5-triisocyanatobenzene and 2,4,6-triisocyanatotoluene, and pentaerythritol 1 for toluene diisocyanate 4 molecule It is an adduct of the molecule. Preference is given to using aliphatic or cycloaliphatic di- or triisocyanates containing 8-36 carbon atoms.

Polyisocyanate and polyisocyanate mixtures prepared by introducing a urethane, allophanate, urea, biuret, carbodiimide, uretonimine or isocyanurate residue may also be used. Examples are triisocyanates such as Tolonate HDT / LV (isocyanurate of hexamethyl diisocyanate) and Vestanate T1890 (isocyanurate of isophorone diisocyanate).

Organic compounds containing at least two isocyanate-reactive groups, having a number average molecular weight of 400 to 6,000 and which can be used to prepare the polyurethane polymer are preferably hydroxyl group terminated polymerizable organic polyols. Organic polyols include in particular diols and triols and mixtures thereof, but higher-functional polyols can be used, for example, as minor components in mixtures with diols. The polyols may be selected from the group of polyesters, polyester amides, polyethers, polythioethers, polycarbonates, polyacetals, polyolefins and polysiloxanes. It is desirable to provide polyols having a number average molecular weight of 700 to 3,000.

Polyester polyols that can be used are polyhydric alcohols such as ethylene glycol, propylene glycol, diethylene glycol, neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, furan dimethanol, dimethylol cyclohexane, glycerol, trimethylol Propane or pentaerythritol or mixtures thereof and polycarboxylic acids, in particular dicarboxylic acids or ester-forming derivatives thereof, such as succinic acid, glutaric acid and adipic acid, or their dimethyl esters, phthalic anhydride, hexahydrophthalic anhydride or dimethyl terephthalate Hydroxy-terminated reaction product. Polyesters obtained by the polymerization of polyols with lactones such as caprolactone can also be used.

Polyester amides can be obtained by including aminoalcohols such as ethanol amines in the polyesterification mixture.

Suitable polyether polyols include poly C ₂ (C ₃ ) alkylene oxide glycols and / or poly C ₂ (C ₃ ) alkylene oxide glycols 1,3-diol, wherein poly C ₂ (C ₃ ) Alkylene oxides represent polyethylene oxides optionally comprising propylene oxide units.

Polythioether polyols that can be used include products obtained by condensing thiodiglycol alone or in combination with other glycols, dicarboxylic acids, formaldehydes, aminoalcohols or aminocarboxylic acids.

Polycarbonate polyols include diols such as 1,3-propane diol, 1,4-butane diol, 1,6-hexane diol, 1,4-cyclohexane dimethanol, diethylene glycol or tetraethylene glycol. Carbonates or dialkyl carbonates, such as diphenyl carbonate, or products obtained by reacting with phosgene.

Suitable polyolefin polyols include hydroxy-terminated butadiene homopolymers and copolymers. An example of a polysiloxane is Tegomer H-Si 2110 from Goldschmidt AG.

To assure that the polyurethane is self-dispersible in water, (a) a single-functional group and / or containing a nonionic and / or ionic disperser (or a group which can be later converted into such disperser) and (c) Or multi-functional isocyanate-reactive compounds are included as reactants in preparing the polyurethane.

Suitable nonionic dispersing groups are the mono C ₁ -C ₄ alkoxy derivatives of the polyether polyols. Preferably, the polyurethane comprises between 2.5 and 20 wt.% C ₁ -C ₄ alkoxy polyC ₂ (C ₃ ) alkylene oxide groups. The number average molecular weight is 500 to 3,000. It is desirable to provide a polyurethane comprising from 5 to 15 wt.% C ₁ -C ₄ alkoxy polyC ₂ (C ₃ ) alkylene oxide groups. Optimal results are obtained with polyurethanes in which the poly C ₂ (C ₃ ) alkylene oxide units are polyethylene oxide units.

Suitable C ₁ -C ₄ polyC ₂ (C ₃ ) alkylene oxide compounds contain at least one hydroxyl group, such as polyethylene oxide monomethyl ether. Examples of diols include methoxy polyethylene oxide-1,3-diol, such as Tegomer D-3123 (PO / EO = 15/85; Mn = 1,180) from Goldschmidt AG, Germany, Tegomer D-3409 (PO / EO = 0/100; Mn = 2,240), and Tegomer (trade name) D-3403 (PO / EO = 0/100; Mn = 1,180). Low molecular weight polyesters containing polyalkylene oxide groups, such as those based on polycarboxylic acids, polyols and adducts of said C ₁ -C ₄ polyC ₂ (C ₃ ) alkylene oxides, can be used. Examples of polycarboxylic acids are dicarboxylic acids or their ester-forming derivatives such as succinic acid, glutaric acid and adipic acid, or their dimethyl esters, phthalic anhydrides, hexahydrophthalic anhydrides or dimethyl terephthalates or mixtures thereof. Examples of polyols include ethylene glycol, propylene glycol, diethylene glycol, neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, furan dimethanol, dimethylol cyclohexane, glycerol, di (trimethylolpropane), trimethyl All propane or pentaerythritol or mixtures thereof. Low molecular weight polyester means a polyester having a number average molecular weight of 1,500 or less.

Suitable ionic dispersants are anionic salt groups, such as carboxylate, sulfonate and / or phosphate (or phosphonate) salt groups, which may be provided for use as reactants in the formation of the polymer. Examples of such compounds are carboxyl groups containing diols and triols, such as dihydroxy alkanoic acid. Preference is given to providing 2,2-dimethylol propionic acid. Sulfonate-based ionic groups are more preferred because they potentially require less basic crosslinking catalyst.

The acid value of the polyurethane containing an ionic dispersing group is 0-25 (solid state), and 5-15 (solid state) are preferable.

If desired, carboxy-containing diols or triols may be added to the polyester by reacting with the dicarboxylic acid prior to addition to the polyurethane.

The conversion of the acid groups present in the polyurethane to anionic salt groups can be carried out by neutralizing the acid groups before, after formation (in combination with nonionic stabilization) or simultaneously with forming the aqueous dispersion of the polymer.

Isocyanate-reactive aldehyde-functional compound (d) includes hydroxymethyl furfural, 5-hydroxy pentanal, 2,5-dimethyl-2-hydroxy adialdehyde, 3 (β-hydroxyethoxy) propanal, β-hydroxyethoxy acetaldehyde and aldol condensation products may be used, such as 3-hydroxybutanal and 3-hydroxy-2-methylpentanal. Thus, optimal results were obtained with 3,7-dimethyl-7-hydroxyoctanal.

The aldehyde functionality of the isocyanate-reactive aldehyde-functional compound can be selectively masked by the formation of lower alkyl (C1-C6) acetals. The unmasking step of the acetal (hydrolysis) can be carried out prior to polyurethane synthesis, after polymer formation or after emulsification. Aromatic aldehyde-inducible resins are less reactive than aliphatic aldehyde-induced resins, and therefore it is preferable to use aliphatic aldehyde-induced polyurethanes.

Organic polyols (e) having a weight average molecular weight of less than 400 which are optionally available at the time of preparation of the polyurethanes include diols and triols, and mixtures thereof, but higher-functional polyols may also be used. Examples of such low molecular weight polyols include ethylene glycol, diethylene glycol, tetraethylene glycol, bis (hydroxyethyl) terephthalate, cyclohexane dimethanol, furan dimethanol, glycerol and the polyol and propylene oxide and / or ethylene oxide There is a reaction product having a molecular weight of 400 or less.

As active hydrogen-containing chain extenders (f), compounds containing groups reactive with free-NCO groups in the polyurethane can be used. Chain extenders are water as well as polyols, polyamines or polythiols. Examples thereof include hydrazine, ethylenediamine, isophorone diamine, 1,2-propane diamine, 1,3-propane diamine, 1,6-hexane diamine, 1,2-ethane dithiol, 1,6-hexane dithiol, 1 , 6-hexane diol- (bis) 3-mercaptopropionate.

The polyurethane dispersions according to the invention comprise at least two having a molecular weight of 400 to 6,000 at substantially anhydrous conditions and a temperature of from about 30 ° C. to about 130 ° C. until the reaction between the isocyanate group and the isocyanate-reactive group is substantially complete. It can be prepared by conventional methods by reacting a polymeric organic compound (b) having isocyanate-reactive groups and other necessary reactants with a stoichiometric amount or excess of organic polyisocyanate (a). In order to control the exothermic reaction, it is desirable to inject the reactants in large scale. If the number of compounds is monofunctional, it is preferred to react them first and then add the multifunctional compound to the reaction mixture in order to obtain the desired molecular weight range. It is more preferable to make compound (a) and (d) react first, and to add compound (c) and (b). If a chain-extended polyurethane is produced, it is advantageous to prepare the isocyanate-terminated prepolymer first. During the preparation of the polyurethane resin or the isocyanate-terminated prepolymer by complete isocyanate conversion, the reactants are isocyanates for isocyanate-reactive groups of about 1: 1 to about 6: 1, preferably about 1: 1 to about 3: 1. Usually used in the ratio of groups. Chain expansion can be performed at high temperature, low temperature, or at ambient temperature. Convenient temperatures are from about 5 ° C to about 95 ° C, or more preferably from about 10 ° C to about 45 ° C.

Polyurethanes incorporating aldehyde functionalities preferably contain aldehyde groups in the polymer in a proportion in the range of 3 to 200 milliequivalents, preferably 6 to 100 milliequivalents per 100 g of polyurethane polymer.

By low molecular weight aldehyde reactive crosslinker compound is meant a compound having a number average molecular weight of 100 to 3,000, preferably 150 to 2,500.

Suitable polyamine compounds include alkylene diamines. As used herein, the term alkylene group means an alkylene group or a cycloalkylene group containing one or more ether-oxygen atoms. Α, ω-alkylenediamine having 2 to 20 carbon atoms in the alkylene group, such as ethylene diamine, propylene diamine, butylene diamine, pentamethylene diamine, hexamethylene diamine, decamethylene diamine, 4,7-dioxadecane- 1,10 diamine, dodecamethylene diamine, 4,9-dioxadodecane-1,12 diamine, 7-methyl-4,10-dioxatridecane-1,13 diamine; 2-methyl piperazine; Cyclohexylene diamines such as 1,2-diaminocyclohexane, 1,4-diaminocyclohexane and 4,4'-diaminodicyclohexyl methane; Isophorone diamine, bis (3-methyl-4-aminocyclohexyl) methane, 2,2-bis (4-aminocyclohexyl) propane, nitrile tris (ethane amine), bis (3-aminopropyl) methylamine, 3 -Amino-1- (methylamino) propane, 3-amino-1- (cyclohexyl-amino) propane, N- (2-hydroxyethyl) -ethylene diamine and the structure H ₂ N- (R ² -NH) _n -R ¹ -NH ₂ , wherein groups R ¹ and n groups R ² are the same or different and represent an alkylene group containing 2-6, preferably 2-4 carbon atoms, n is 1-6, preferably Preferably 1-3). Again, the term alkylene group may also mean an alkylene group or a cycloalkylene group containing an ether-oxygen atom. Examples of such polyalkylene polyamines are diethylene triamine, dipropylene triamine, dibutylene triamine, Jeffamine (trade name) T403 from Huntsman, trisaminomethylamine, and 5-aminomethyl octane diamine-1,8 . It is preferred that the polyamines according to the invention are (ring) aliphatic and contain 5-15 carbon atoms, such as isophorone diamine; In particular the polyamines should contain α-alkyl groups such as bis (3-methyl-4-aminocyclohexyl) methane and bis (3-methyl-4-aminocyclohexyl) propane. Other suitable polyamines are by hydrogenation of polynitro compounds disclosed in EP-B-0 678 105, or by hydrogenation of polynitriles obtainable by Michael addition reaction of polyols or polythiols with acrylonitrile. Adducts of (poly) amino compounds to obtainable compounds or polyfunctional epoxy, isocyanate, maleate, fumarate or (meth) acryloyl compounds. Thus, the crosslinking agent used was a hydrogenated reaction product of 3- [2,2-bis- (3-amino-propoxymethyl) -butoxy] -propylamine, ie, Michael adduct of 3 moles of trimethylol propane and acrylonitrile. Very good results were obtained when.

Structural formulas E ¹ -CHR ¹ -E ² , wherein -E ¹ and -E ² are electrons such as -P (= 0) -O-, -CO-, -CN, -SO _2- , and -NO ₂ , respectively. Examples of suitable low molecular weight aldehyde-reactive crosslinkers, which are selected from protractors and R ¹ represents a hydrocarbon radical or hydrogen having 1 to 10 carbon atoms, are -CO-CHR ¹ -CO-, NC-CHR ¹ -CO-, -OP (= O) -CHR ¹ -CO-, -OP (= O) -CHR ¹ -P (O =)-O- and -CO-CHR ¹ -NO ₂ Compound.

Examples of R ^{1 which} is a hydrocarbon radical are alkyl groups having 1 to 10 carbon atoms, such as methyl group, ethyl group, propyl group and butyl group.

The low molecular weight aldehyde-reactive crosslinking agent is an alkyl of the acid having 1-6 carbon atoms in an acid radical such as acetoacetic acid, acetone dicarboxylic acid, phosphonic acid, cyanoacetic acid and malonic acid, and an alkyl radical such as methyl, ethyl and n-butyl Substituted or aryl-substituted derivatives such as α-methyl acetoacetic acid and γ-methyl acetoacetic acid, or alkyl-substituted or aryl-substituted derivatives having 6-10 carbon atoms in an aryl radical such as phenyl, ketone, (Partial) amides of such acids such as acetyl acetone, benzoyl acetone or acetyl dibenzoyl methane, and acetoacetamide.

Also included are (partial) esters of the acids. Suitable alcohols for esterification of such acids are monohydric alcohols and polyhydric alcohols. Monohydric and polyhydric alcohols are well known, and any known compound may be used. Preferably, the alcohol contains 1 to 50 carbon atoms, more preferably 1 to 15 carbon atoms. Examples of alcohols include methanol, ethanol, butanol, octanol, ethylene glycol, propylene glycol, trimethylol ethane, trimethylol propane, 1,2,6-hexane triol, glycerol, diethylene glycol, 2,2'-bis- 4-dihydroxyphenyl propane, 1,5-pentane diol, pentaerythritol, polyoxy produced by reaction of alkylene oxides with polyalcohols, for example ethylene oxide or propylene oxide with ethylene glycol Alkylene polyols; Trifunctional products, such as those resulting from the reaction of propylene oxide with glycerol; Polycaprolactone polyols such as compounds resulting from the reaction between propylene glycol and ε-caprolactone; And α-ω-dihydroxy (alkyl) polysiloxanes.

Some of the alkyl-substituted esters, for example α-methyl acetoacetic acid esters or α, γ-dimethyl acetoacetic acid esters contain only one active H atom, so that a sufficient number of reactors can be used to Preference is given to using in the form of diesters or diamides or polyesters of alcohols or polyamides or polyamines.

Other examples of suitable compounds are the reaction products of these acids with (poly) acrylates, polyesters, polyethers, polyester amides, polyester imides and polyhydroxyl amines. Also included are nitriles based on acetoacetic acid, phosphoric acid and / or malonic acid, such as malonic acid mononitrile or dinitrile.

It is desirable to provide low molecular weight polyacetoacetate compounds obtainable by reacting diketene or alkyl acetoacetates with polyols having two or more hydroxyl groups. Examples of suitable non-polymerizable poly-acetoacetates or alkyl-acetoacetates include trimethylol propane triacetoacetate, trimethylol ethane triacetoacetate, ethane diol bisacetoacetate, trimethylol propane triacetoacetate, 1,2,6-acetate. Hexane triol triacetoacetate, bisacetoacetate of diethylene glycol, bisacetoacetate of 2,2'-bis-4-hydroxyphenyl propane, 1,5-pentanediol diacetoacetate, and pentaerythritol tetraacetoacetate There is.

Structural formula HC- (E ¹ E ² E ³ ), wherein -E ¹ , -E ² and -E ³ are -P (= 0) -O-, -CO-, -CN, -SO ₂ -,- Examples of aldehyde-reactive crosslinking agents each selected from an electron withdrawing group such as NO ₂ , wherein R ¹ represents a hydrocarbon radical or hydrogen having 1 to 10 carbon atoms) are made of methane triscarboxylic acid or esters thereof Esters.

The reaction between a low molecular weight aldehyde-reactive crosslinker and an aldehyde-functional polyurethane comprising at least one group of one of the structural E ¹ -CHR ¹ -E ² and HC- (E ¹ E ² E ³ ) has a pKa of at least 9 It is carried out in the presence of a basic catalyst. Preferred compounds are amines in the form of amidine, for example tetramethyl guanidine, 1,4-dihydropyrimidine, 1,8-diaza-bicyclo [5.4.0] undec-7-ene, 1,4- Adducts of epoxy compounds to diazabicyclo- [2.2.2] octane, 2-alkyl-N-alkyl imidazolines, and tertiary amines, such as Epikote 828 (trade name) (manufactured by Shell) and 1,4-diaza A reaction product of bicyclo [2,2,2] octane.

Other preferred catalysts include quaternary ammonium compounds such as quaternary ammonium hydroxides such as tetrabutyl ammonium hydroxide; Quaternary ammonium alkoxides such as benzyl trimethyl ammonium methoxide and dilauryl dimethyl ammonium methoxide; And quaternary ammonium carbanions such as benzyl trimethyl ammonium acetyl acetate. The amount used is 0.05 wt.% To about 10.0 wt.%, Preferably about 0.05 wt.% To about 6 wt.%, More preferably about 0.1 wt., Based on the combined weight (solid state) of component (A) and (B). And from about 4.0 wt.%.

The reaction between the aldehyde-functional polyurethane and the low molecular weight polyamine crosslinker can be carried out without a catalyst.

Preferably, the aldehyde-functional polyurethane equivalent ratio of the low molecular weight aldehyde-reactive crosslinking agent based on the aldehyde-reactive group of the low molecular weight crosslinker and the aldehyde group of the polyurethane is 0.5: 1 to 5: 1.

The aqueous crosslinker composition according to the present invention is prepared by dispersing dissolved or dispersed polyurethane in an organic solvent in water and then evaporating all or most of the remaining solvent. The crosslinker can be mixed into the polyurethane solution or dispersion by any suitable method. However, simple agitation is usually sufficient. Sometimes it is also possible to dilute the binder solution or dispersion with an organic solvent such as ethyl acetate or 1-methoxy-2-propyl acetate to lower the viscosity.

If a catalyst is used, the catalyst is added to an aldehyde-functional polyurethane emulsion which may or may not already contain an aldehyde-reactive functional crosslinker.

The composition of the present invention, which is an aqueous composition, essentially comprises water. However, about 20 wt.% Of the liquid content of the composition is an organic solvent. Suitable organic solvents include dimethyl dipropylene glycol, methyl ether of diacetone alcohol, ethyl acetate, butyl acetate, ethyl glycol acetate, butyl glycol acetate, 1-methoxy-2-propyl acetate, butyl propionate, ethoxyethyl prop Cypionate, toluene, xylene, methylethyl ketone, methylisobutyl ketone, methylamyl ketone, ethylamyl ketone, dioxolane, N-methyl-2-pyrrolidone, dimethyl carbonate, propylene carbonate, butyrolactone , Caprolactone and mixtures thereof. The VOC of the composition is 0 to 400 g / l, preferably 0 to 250 g / l.

The binder composition according to the invention comprises mixtures of other aldehyde-functional polyurethanes and mixtures of low molecular weight aldehyde-reactive crosslinkers.

The membrane obtained from the composition does not bubble at a thickness of at least 60 μm or less.

Preferably, the composition according to the invention is a two-component composition in which component (A) is an aqueous dispersion of aldehyde-functional polyurethane and component (B) is non-aqueous. More preferably, component B is used as a low viscosity resin, so there is no solvent and no water.

For use in coating compositions, the binder composition may contain other binder components, pigments, waxes, solvents, flow additives, neutralizers, defoamers, wetting agents, dyes, emulsifiers (surfactants), pigment dispersion aids, leveling agents, anti-wrinkle preparations. Unsaturation capable of reacting with one or more of anti-cratering agents, anti-foaming agents, anti-sagging agents, heat stabilizers, UV absorbers, light stabilizers, anti-oxidants and fillers And other components, additives or auxiliaries such as polymer dispersions or other polymers with or without a (meth) acrylate group or a reactor such as epoxy. Other suitable polymer dispersions are acrylic polymer emulsions and aqueous polyurethane dispersions.

The coating composition of the present invention can be applied to any substrate. Examples of substrates are metal, plastic, wood, glass, ceramic or some other coating layer. The other coating layer may include the coating composition of the present invention, or may include another coating composition. Coating compositions of the present invention exhibit particular utility as clearcoats, basecoats, colored topcoats, primers and fillers. The coating composition may be applied by conventional means, such as a spray gun, brush or roller, with spraying being preferred. The curing temperature is preferably 0 to 80 ° C, and more preferably 20 to 60 ° C. The composition is used in the manufacture of coated metal substrates, such as in the refinishing industry, for repairing automobiles and vehicles, especially in body shops, and for coating large vehicles such as trains, trucks, buses and airplanes. It is particularly suitable for finishing. The coating composition is preferably used as a primer.

The invention will be explained in more detail with reference to the following examples. Of course, the embodiments are only for better understanding of the present invention; Neither way is considered to limit the scope of the invention.

In this example, a process for preparing a plurality of aqueous polyurethane dispersions and binder compositions according to the present invention is disclosed. Dispersions were characterized by their solid content, molecular weight, viscosity and particle size. The average particle size of the dispersion was measured by Coulter LS230 particle size analyzer. Viscosity was measured by Brookfield CAP 2000 (LV-4; 60 revolutions per minute). Solid content was measured according to ASTM method 164-59 by Sartorius MA 30 humidity analyzer at a temperature of 140 ° C.

Molecular weight measurements were carried out by gel permeation chromatography on a Waters 2690 instrument equipped with Polymer Laboratories, column type PL1000 and Waters 2410 refractometer detector unit. Tetrahydrofuran with 0.5% by weight acetic acid was provided as eluent. The system was calibrated by polystyrene standards.

Preparation of Aldehyde-functional Aqueous Polyurethane Dispersion

Polyurethane Dispersions 1

a) The four-necked 2 L flask was equipped with a variable speed stirrer, thermocouple in combination with a regulator, a distillation column, a cooler, a nitrogen sparge and a heating mantle. Into the flask was added 836.0 g of hexahydrophthalic anhydride, 962.5 g of 1,6-hexanediol and 0.45 g of dibutyl tin oxide. The mixture was heated at 250 ° C. with stirring under nitrogen flow and kept at this temperature for 4 hours while distilling off the water. The mixture was then cooled to room temperature. A clear colorless polyester 1a having an acid value of 1.6 mg KOH / g, a hydroxyl value of 179 mg KOH / g, and GPC data Mn 990, Mw 1600 was obtained.

b) The four necked 5 L flask was equipped with a variable speed stirrer, thermocouple in combination with regulator, cooler, nitrogen inlet and outlet, and heating mantle. Into the flask was placed 71.3 g of isophorone diisocyanate, 54.4 g of trimer of hexamethylene diisocyanate (Tolonate HDT LV made by Rhodia), 49.1 g of 3,7-dimethyl-7-hydroxyoctanal and 162.8 g of 2-butanone. . The mixture was stirred until homogeneous, and then 0.19 g of tin (II) octanoate was added. The reaction is exothermic and further heated to 80 ° C. and maintained at this temperature for 6 hours. The isocyanate content of the mixture was then 7.9%. The reaction mixture was cooled to 30 ° C., 46.7 g of polyethylene oxide glycol (Mn = 1,180; Tegomer D3403 manufactured by Tego Chemie Service), 157.8 g of polyester diol 1a and 4.5 g of dimethylol propionic acid were added, followed by tin ( II) 0.19 g of octanoate was further added. The mixture was further heated to 80 ° C. for 4 hours, after which the isocyanate content of 0.1% or less was measured. The mixture was cooled to 45 ° C. and 3.03 g of dimethyl ethanolamine were added. The stirrer was set to maximum speed and 690 g of water was added at a rate of 10 ml / min. When the water addition was complete, the distillation head and vacuum pump were connected to the flask and the pressure was gradually lowered until all 2-butanone was distilled off.

A white emulsion having the following characteristics was obtained: solid content 35%, Mn 3,310, Mw 19,000, viscosity 36 mPas, pH 8.6, particle size 134 nm.

Aldehyde equivalent: 1,333 g / eq (solid), EO content: 10% (solid)

Polyurethane Dispersions 2

a) Polyester diol 2a was prepared in a similar manner to that described for preparing polyurethane dispersion 1 under the conditions that 719.1 g of hexahydrophthalic anhydride, 1,064.5 g of dimethylol cyclohexane and 0.45 g of dibutyl tin oxide were added. Prepared. The mixture was heated to 250 ° C. with stirring under nitrogen flow and maintained at this temperature for 4 hours while distilling off water. Then the mixture was cooled to room temperature. A clear colorless polyester having an acid value of 0.4 mg KOH / g, a hydroxyl value of 179 mg KOH / g, and GPC data Mn 910, Mw 1,430 was obtained.

b) 57.9 g of isophorone diisocyanate, 59.7 g of trimers of isophorone diisocyanate (Vestanat (trade name) T1890 from Creanova), 42.2 g of 3,7-dimethyl-7-hydroxyoctanal and 138.4 g of 2-butanone Under the conditions of adding the components, an aldehyde-functional polyurethane dispersion was prepared in a manner similar to that described for preparing polyurethane dispersion 1. After the mixture was stirred until homogeneous, 0.16 g of tin (II) octanoate was added. The reaction was exothermic and was further heated to 80 ° C. and maintained at this temperature for 6 hours. The isocyanate content of the mixture was then 6.9%. The reaction mixture was cooled to 30 ° C., and 36.6 g of polyethylene oxide glycol (Mn = 1,180; Tegomer D3403 manufactured by Tego Chemie Service), 126.1 g of polyester 2a and 3.9 g of dimethylol propionic acid were added, followed by tin (II). ) 0.16 g octanoate was further added. After further heating the mixture to 80 ° C. for 4 hours, an isocyanate content of 0.1% or less was measured. The mixture was cooled to 45 ° C. and 2.58 g of dimethyl ethanolamine were added. The stirrer was set to maximum speed and 600 g of water were added at a rate of 10 ml / min. When the water addition was complete, the distillation head and vacuum pump were connected to the flask and the pressure was gradually lowered until all 2-butanone was distilled off.

A white emulsion having the following characteristics was obtained: solid content 36%, Mn 5,580, Mw 17,800, viscosity 24 mPas, pH 8.3, particle size 159 nm.

Aldehyde equivalent: 1,333 g / eq (solid), EO content: 10% (solid)

Preparation of Low Molecular Weight Aldehyde-Reactive Crosslinkers

Preparation of 3- [2,2-bis- (3-amino-propoxymethyl) -butoxy] -propylamine (polyamine crosslinker)

a) The four-necked 1 l flask was equipped with a variable speed stirrer, thermocouple in combination with regulator, cooler, nitrogen inlet and outlet, addition funnel and heating mantle. 48.0 g of trimethylol propane was added to the flask, and the whole was heated to 60 ° C. Thereafter, 0.024 g of sodium methoxide was added to the melt. 57.9 g of acrylonitrile was added for 1 hour. The exothermic reaction was maintained at 60 to 70 ° C. by external cooling. After cooling to room temperature, traces of precipitate were removed by vacuum filtration. ¹ H-NMR analysis of the intermediate showed 97% conversion of all hydroxyl groups. The intermediate had a color of less than 1 Gardner.

Hydrogenation of the intermediate obtained in b) a) was carried out in a 2 L stainless steel autoclave with hydrogen and NH ₃ injectors, pitch blade stirrers and baffles for proper mixing. In the autoclave was placed 201.8 g of a 50 wt.% Solution in 2-propanol of the adduct and 5 g of Raney cobalt. Thereafter, 15 g of gaseous NH ₃ was placed in an autoclave and subsequently heated to 100 ° C. Hydrogen was then placed in the reactor and maintained at a total pressure of 50 bar. The hydrogenation continued for 2 hours, during which the reaction temperature gradually increased to 150 ° C. After cooling to room temperature, the cobalt catalyst was removed by distillation and the filtrate was concentrated in a rotary evaporator until all 2-propanol was distilled off.

Polyamine was obtained as a liquid having an amine value of 500 mg KOH / g. The liquid was diluted with water to give a clear solution with Gardner color 2 and a solids content of 50 wt.%.

Preparation of Coating Composition

To coating composition A consisting of 20.1 g of polyurethane dispersion 1 and 19.1 g of polyurethane dispersion 2, 1.3 g of trimethylol propane triacetoacetate, 5.6 g of tetrabutyl ammonium hydroxide (TBAH as a 10% aqueous solution) and 0.20 g of BYK 346 as a wetting agent Was added. The equivalent ratio of aldehyde group to acetoacetate group was 1: 1.

To coating composition B consisting of a mixture of 20.1 g of polyurethane dispersion 1 and 19.1 g of polyurethane dispersion 2 was added 2.2 g of the polyamine crosslinker and 0.21 g of BYK 346 as a wetting agent. The equivalent ratio of aldehyde groups to amine groups was 1: 1. Both compositions were applied on tinned panels with a dry layer thickness of 80 μm (composition A) and 110 μm (composition B), respectively. The panels were dried at ambient temperature (room temperature) for 1 day.

Persoz Hardness of the obtained coating layer was measured according to the French industrial standard method NF T30-016, and the results are expressed in seconds.

Resistance to methylethyl ketone (= 2-butanone) and water was measured by exposure for 1 minute (methylethyl ketone) after 1 day or 7 days of maturation or 1 hour of exposure (water) after 7 days of maturation.

Properties of the coating layer obtained are shown in Table 1.

In the resistance test, 0 indicates dissolution, 3 indicates slight influence, and 5 indicates excellent.

All coating layers showed good water resistance.

Composition 7 days aging hopper sauce hardness (sec) Resistance to methyl ethyl ketone (MEK) after aging for 2 days Resistance to methyl ethyl ketone (MEK) after aging for 7 days Water resistance after aging for 7 days A 59 3 3 5 B 34 3 3 5

Claims (13)

(A) an aqueous dispersion of an aldehyde-functional polyurethane, wherein the polyurethane comprises an ionic and / or non-ionic disperser, and has a number average molecular weight of at least 1,000 and an average aldehyde functionality of at least two, and (B) Structural Formulas E ¹ -CHR ¹ -E ² and HC- (E ¹ E ² E ³ ), wherein -E ¹ , -E ² and -E ³ are each -P (= 0) -O-, Is selected from an electron withdrawing group such as -CO-, -CN, -SO _2- , -NO _2, and R ¹ represents a hydrocarbon radical having 1 to 10 carbon atoms or hydrogen; An aqueous crosslinker composition comprising a low molecular weight aldehyde-reactive crosslinking agent selected from the group of low molecular weight compounds and low molecular weight polyamines. The method of claim 1, The crosslinking agent comprises an acetoacetate group. The method according to claim 1 or 2, The number average molecular weight of the aldehyde-functional polyurethane is an aqueous crosslinker composition, characterized in that in the range of 1,000 to 100,000. The method according to any one of claims 1 to 3, The polyurethane is a) organic polyisocyanates, b) organic compounds containing at least two isocyanate-reactive groups and having a number average molecular weight of 400 to 6,000, c) (a) single-functional and / or multi-functional isocyanate-reactive compounds containing nonionic and / or ionic dispersers (or groups which can be later converted into dispersers), d) isocyanate-reactive aldehyde-functional compounds, e) optionally, an organic polyol having a weight average molecular weight of less than 400, and f) optionally, an aqueous crosslinker composition, obtainable by reaction of an active hydrogen-containing chain extender. The method of claim 4, wherein Wherein said ionic dispersing group is an anionic dispersing group selected from the group of carboxylate, sulfonate and / or phosphate (or phosphonate) salt groups. The method of claim 4, wherein An aqueous crosslinker composition, wherein the C ₁ -C ₄ alkoxy poly C ₂ -C ₃ alkylene-oxide group is used as a nonionic dispersant in an amount of 2.5 to 20 wt. The method of claim 6, Wherein said C ₁ -C ₄ alkoxy poly C ₂ -C ₃ alkylene-oxide group is used in an amount of 5 to 15 wt.%. The method according to any one of claims 1 to 7, Based on the aldehyde-reactor of the low molecular weight crosslinker and the aldehyde group of the polyurethane, the equivalent ratio of the aldehyde-functional polyurethane to the low molecular weight aldehyde-reactive crosslinker is 0.5: 1 to 5: 1. The method according to any one of claims 2 to 8, The acetoacetate crosslinking agent is selected from the group of trimethylol propane triacetoacetate and trimethylol ethane triacetoacetate. The method according to any one of claims 1 and 3 to 8, Polyamine crosslinkers are adducts of (poly) amino compounds to α, ω-alkylenediamines having 2 to 20 carbon atoms in alkylene groups, cyclohexylene diamines, 2-methyl piperazine, isophorone diamines, polyfunctional epoxy , Isocyanate, maleate, fumarate or (meth) acryloyl compound and hydrogenated polynitro or polynitrile compound. The method of claim 10, Wherein said polyamine crosslinking agent is 3- [2,2-bis- (3-amino-propoxymethyl) -butoxy] -propylamine. Use of the binder composition according to any one of claims 1 to 11, which is used to prepare a primer composition or a clear coat composition. Use of the binder composition according to any one of claims 1 to 11, which is used for repainting of motor vehicles.